This invention relates generally to computerized optimization of electronic circuits and more particularly to the selection of various field-effect transistor (FET) width-to-length ratios or bipolar transistor areas for circuit optimization.
Computerized optimization of electronic circuits may involve adjusting a set of circuit parameters (i.e. resistor values, FET sizes, etc.), running a simulation to see if the new values have improved a performance parameter (i.e. bandwidth, amplification, circuit delay), and selecting a new set of parameters based upon the results of the simulation and some search algorithm. This process may continue until a desired result is achieved (i.e. the performance parameter reaches or exceeds a certain value) or until all of a set of circuit parameters has been tried (i.e. an exhaustive search).
Typically, when optimizing a circuit for use on an integrated circuit, the primary circuit parameters that may be adjusted are the sizes (i.e. the width-to-length ratios of the FETs, or the area of the bipolar transistors) of the transistors in the circuit. Some of the methods for picking adjusted sizes for a transistor include picking a totally random value from a specified range or picking a size that is linearly different from the original value resulting in a set of values that may be evaluated that is linearly distributed a specified range. One problem with picking a random transistor size is that a large number of random values may need to be evaluated before an optimal value is found. Also, using random values may yield a different result each time the optimization is run so this method does not necessarily produce a deterministic result. One problem with picking a value that differs linearly from the original value is that it may take a great number of iterations to reach an optimal value that lies far from the initial transistor size.
A set of discrete transistor sizes spread in an exponential manner over a specified range is the basis for adjusted transistor sizes used to optimize a circuit. One of the discrete transistor sizes may be the original transistor size or other starting point for the optimization.